1. Field of the Invention
The present invention relates to a cosmetic O/W emulsion comprising
a) 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (INCI: octocrylene),
b) 4-(tert-butyl)-4′-methoxydibenzoylmethane (INCI: butyl methoxydibenzoyl methane),
c) licorice extract or licochalcone A, and the preparation and use thereof.
2. Discussion of Background Information
The skin is the largest organ belonging to humans. It has a large number of vital functions to fulfill, for example the regulation of heat and the barrier function against drying out of the skin and of the entire organism, and as protective equipment against the penetration and absorption of external substances. This barrier function is effected through the epidermis, which as the outermost layer forms the actual protective covering against environmental conditions. With about one tenth of the total thickness, at the same time, it is the thinnest layer of the skin.
The skin is exposed to a large number of physical, chemical and biological stresses. A large number of these stresses lead to temporary or permanent reddening of the skin for various reasons.
So that the skin can fulfill its biological functions, it requires regular cleansing and care. In order to promote regeneration of the skin, to protect it from premature ageing or to avoid irritation, active ingredients are as a rule added to cosmetic skin care products.
The active ingredients employed in skin care include, for example, licorice extracts. The key active ingredient of licorice extract, in particular of Glycyrrhiza inflata, in this context is the compound licochalcone A, which has the following structure:
Licochalcone A
Licorice extracts containing licochalcone A are employed in this context in particular to protect against skin irritations, such as reddenings.
A disadvantage of the prior art of cosmetic formulations containing licorice extracts (especially if these extracts contain licochalcone A) is, however, the fact that the extracts and in particular licochalcone A are not particularly storage-stable. If these formulations are stored for a relatively long period of time, and in particular at higher temperatures, degradation of the active ingredient(s) in the formulation occurs and the cosmetic slowly loses effectiveness. This loss in effectiveness occurs to a particularly high degree in O/W emulsions (oil-in-water emulsions).
It was therefore the object of the present invention to eliminate the disadvantages of the prior art and to develop storage-stable or heat-stable cosmetic formulations which contain licorice extracts or licochalcone A.
It was moreover the object of the present invention to develop a formulation which is easy and inexpensive to prepare.